1. Field of the Invention
The invention relates to a method of electrically conductively connecting two superconductive cables, which each comprise at least two concentrically arranged conductors surrounded by a dielectric, and an electrically effective screen mounted above the outer dielectric, by means of which the conductors and screens to be connected are initially freed of surrounding layers and subsequently electrically conductively connected to each other (EP 1 552 536 B1).
2. Description of Related Art
Superconductive cables have been known for a long time in different embodiments. This is basically also applicable to technologies for electrically connecting two superconductive cables. A significant difference of the superconductive cables relative to the conventional cables resides in the fact that the cables have electrical, conductors of a material which at sufficiently low temperatures chances over into the superconductive state, with a direct current resistance which approaches zero. Suitable superconductive materials are, for example, oxidic materials on the basis of rare earths. Sufficiently low temperatures for placing such a material into the superconductive state are, for example, between 67K and 110K. Suitable cooling agents for all these materials are, for example, nitrogen, helium, neon and hydrogen, or mixtures of these materials. When operating a transmission length for electrical energy with at least one superconductive cable, the cable is arranged in accordance with known technology in a cryostat which consists of at least one thermally insulated pipe, through which, when operating the transmission length, a cooling agent suitable for a superconductive material used is conducted, advantageously one of the cooling agents mentioned above.
In transmission lengths of electrical energy two or more lengths of a superconductive cable must be connected to each other electrically conductively. This means that the conductors and the screens of the two cables are initially freed of surrounding layers. After the electrically conductive connection of two conductors of the two cables, the removed layers, i.e. essentially the dielectrics, must be reapplied. This is achieved, for example, essentially by winding bands of insulation material onto the entire connecting point including the two conductors. Subsequently, the conductors located thereabove and the screens can also be electrically conductively connected and can be insulated in the same manner. This is already very complicated and time consuming in the case of only one conductor and a screen, and it also requires the use of technically skilled personnel. In the case of a cable with two or three conductors which are arranged concentrically to each other and are insulated relative to each other, as disclosed for example in the above mentioned. EP 1 552 536 B1, the applied labor is extremely high, especially since it must be safely ensured that the wall thickness of the reconstructed insulation or insulations may not be significantly greater than the original wail thickness. It is only then that the dimensions of a cryostat are kept so small that they do not impair the operation of the transmission length, particularly the flow of the cooling agent through the cryostat.